Some weird results at input . I think windows is to blame here . Here's what happens : I want to creating a bunch of sattelites using the instruction : start,end in the sma field around the primary star . In the range 0.5 to 1 au ( inoput 0.5,1) . Instead of getting a stable orbt I get a weird pattern , as shown here Is it possible that the instruction 0.5,1 is misinterpreted by windows?

Since you have a double sun, you must check the 'barycenter' option under "Reference object" in the Create Objects interface. That's because to a distant particle, it is orbiting 2 solar masses, but without the 'barycenter' option, Gravity Simulator is computing its orbital velocity assuming it is orbiting around 1 solar mass.

Then on the Graphics Options interface, you must press the F/A button so that it reads "A". That tells Gravity Simulator to focus on the barycenter rather than on the Sun.

Thanks Tony , this works . Thought Windows conversion was responsible but it isn't . Fortunately . But I discovered something odd . If I create an output file I see the SMA of the bodies being negative , although they are in a "normal" orbit around the binary . Is it possible for you to chech this ?

That's because its giving you the sma with respect to the reference object, probably the Sun, rather than wrt to the barycenter. At the moment, there's no way around this. I'd have to code a new routine. If you're clever with Excel, you can always compute the orbital elements yourself using the position and velocity vectors.